The invention concerns an ejector apparatus for an injection molding machine, including ejector pins mounted to a movable ejector plate and drivable by a drive device for ejecting injection molded parts from a cavity of an injection molding tool. The ejector plate is displaceable by the drive device with a given normal ejector force acting on an injection molded part.
Apparatuses of that kind serve for the ejection of semi-solidified or entirely solidified injection molding parts from the cavity. Particularly if the injection molded product has portions of an undercut configuration, problems can however arise upon ejection. An example of such injection molded products are screw caps for drink bottles, which have a female screwthread. In order to release them from the negative portion (with a male screwthread) of the injection molding tool, ejector pins strip the injection molded part which has not yet entirely hardened from the one tool half of the injection molding tool. As the plastic material has not yet entirely set, the screw cap widens and can thus be stripped over the negative screwthread of the cavity-forming tool half and thereafter is restored to the original shape.
If delays, interruptions or alterations occur during an injection cycle, however, it the injection molded product can harden to an excessive degree, whereby stripping removal thereof is only possible with greater difficulty, and jamming occurs in the ejection procedure. That results in a stoppage in the ejection operation, which can be released for example by manually turning the jammed injection molded product out. It will be noted, however, that this is a highly time-consuming and ineffective operation.
The object of the invention is to avoid the above-described disadvantages and to provide an ejector apparatus which is more effective and improved over the state of the art.